Sony Pictures has denied Spider-Man 3 has been pirated, and claims copies being sold in China are actually fake.
Spider-Man will be released in China before the US
Street vendors have been found selling DVDs in the Spider-Man 3 sleeve for 10 Yuan (65p), ahead of the film's cinema release in China on 1 May.
Reuters discovered some copies featured the 2001 TV movie Earth vs The Spider, starring Dan Aykroyd, while Sony says some show Spider-Man 2 instead.
Sony said "similar hoaxes and false alarms" often occur before releases.
"Our investigation in China has revealed no case of the film being pirated to date," said Sony.
The company also suggested no evidence has been found that the film has been pirated online.
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"This incident underscores one of the problems with piracy - people who buy illegal movies often get ripped off themselves," Sony added.
In recent weeks China has hit back at the US over complaints made to the World Trade Organisation that it is not doing enough to tackle piracy.
The media has been invited to high-profile events to watch millions of pirated DVDs, music CDs and software being crushed.